The field of the present invention is thermal processors for semiconductor articles.
Furnaces are used in the processing of semiconductor articles such as wafers. Chemical deposition, etching and the like are conducted in such furnaces through the injection of reactants into a process chamber within which the semiconductor articles are positioned.
Heating of reactants prior to introduction into the process chamber is frequently used to convert the reactant into a gaseous or vapor state, heat the reactant to near the interior temperature of the furnace, and/or chemically transform a precursor into an appropriate reactant for the process. The application of these reactants typically is advantaged by a continuous flow into the furnace during operation. Consequently, a steady state flow is advantageously achieved and one which provides sufficient residence time before entry into the process chamber for complete reactions, thermal equilibration with the interior of the furnace and the like.
Devices have been developed to increase residence time within an injector prior to introduction of the reactants into the furnace process chamber. Long and circuitous paths and paths of greater cross sectional area have been proposed for extended residence time. However, the presence of the cooler materials and the presence of the injectors themselves can have a deleterious effect on the uniformity of the thermal environment in the process chamber.
The reactants may be preconditioned outside of the process chamber. In such circumstances, column heaters may be employed to mix gas, reactant(s) and heat before introduction into the furnace itself. Such column heaters have been thought most efficient when flow is from top to bottom. However, thermal isolation from the furnace itself can create difficulties where an extended path is required from the bottom of the column heater to the heated environment of the process chamber.